My acer 7520 opens with an error reading NVIDIA

This error message could be a faulty hard disk or a faulty disk controller.
Reseat the hard disk to see if the problem is fixed.
If not go into the BIOS settings and check if the BIOS can detect the hard disk.
If the hard disk is not detected then remove the hard disk and connect it to an USB hard disk adapter and connect it to a working computer's USB port. If the this computer cannot detect it as an external hard drive then the hard drive is faulty. Then the Acer needs a replacement hard disk and Windows installed together with the laptop's device drivers and programs etc.